The greatest hassle with reinvesting dividends and capital gains distributions (and DRIP programs) is the large number of transactions generated. Each share you sell has an associated cost. So your calculation of cost basis can become complex. It is definitely more complicated than if you bought 100 shares of IBM twenty years ago.

A spreadsheet program is an easy way to add up all of those purchases and make sure you have them entered correctly. But you will probably spend a few hours at it if you have owned the mutual fund for years.